CONTENTS OF PART I 







1. Introduction 5 



2. Nomenclature 7 



3. General review of the literature 9 



4. The comparative morphology of the pineal region 17 



1. In cyclostomes 21 



2. In selachians 23 



3. In ganoids 25 



4. In teleosts 27 



5. In dipnoi 29 



6. In amphib'a 30 



7. In reptilia 31 



8. In aves 36 



9. In mammals 37 



5. The comparative embryology of the epiphyseal complex 39 



1 . In cyclostomes 39 



2. In selachians 41 



3. In ganoids 48 



4. In teleosts 50 



5. In amphibia 53 



6. In reptilia 56 



7. In aves 67 



8. In mammals 72 



6. The comparative anatomy and histology of the epiphyseal complex 80 



1 . In cyclostomes 80 



2. In selachians 92 



3. In ganoids 98 



4. In teleosts 103 



5. In amphibia 114 



6. In reptilia 119 



7. In aves 148 



8. In mammals 155 



7. Discussion 196 



1. Significance of the pineal region 196 



2. Evidence based on the gross morphology of the epiphyseal complex 203 



a. Phyletic constancy 203 



b. Phyletic variation and morphologic specialization 205 



c. Relative constancy of the epiphyseal complex with reference to 



other structures of the pineal region 211 



d. Relative constancy of the epiphyseal complex with predomi- 



nance of the proximal portion 211 



3 



